1. Field of the Invention
The present invention relates to a method for manufacturing an antireflection function-equipped lens and particularly to a method for manufacturing an antireflection function-equipped lens having one surface provided with a non-reflective coating consisting of a dielectric multilayer film and the other surface provided with a structured non-reflective coating.
2. Description of the Related Art
In the related art, in optical elements (lenses) in which translucent media such as glass media and plastic media are used, when surface reflection frequently occurs, flares or ghosts are frequently generated, and the transmittance decreases, and thus antireflection films made of thin dielectric films are provided on the surfaces. These antireflection films are required to be capable of producing favorable antireflection effects even when the incidence angle ranges of the fluxes of light incident on optical elements are wide. In order to obtain strong antireflection effects in wide incidence angle ranges, it is required that the difference in refractive index between films constituting interfaces between the air and a layer or between a layer and a layer is small. As methods for realizing small differences in refractive index, structured non-refractive coating in which antireflection functions are imparted by forming fine unevenness that is equal to or smaller than the wavelengths of visible light on surfaces is known (JP2005-275372A and the like).
Meanwhile, antireflection films having uneven structures have broad spectra and are capable of suppressing reflectance at low levels with respect to light rays at low to high angles, but have a problem of weak wear resistance due to their uneven shapes.
JP2010-269957A discloses a lens having a dielectric multilayer film formed on one surface and an uneven structure film formed on the other surface using boehmite. In Example 2 in JP2010-269957A, a manufacturing method in which a dielectric film is formed on one surface of a lens, and then an alumina film is formed on the other surface and is then immersed in hot water, thereby forming a fine uneven structure film is employed.
JP2011-145627A discloses a method in which, in a state in which one surface remains non-coated (non-treated), an alumina film is formed on the other surface, and then a hot water treatment is carried out, thereby forming a fine uneven structure film. Although there is no description of any treatments after the formation of the fine uneven structure film in JP2011-145627A, when a dielectric multilayer film is formed on one surface after the formation of the fine uneven structure film, it is possible to obtain lenses having an antireflection film consisting of a dielectric multilayer film on one surface and an antireflection film consisting of a fine uneven structure film on the other surface.